Sound dampening properties are found in materials with a high sound transmission loss. The sound transmission loss of a material is determined by various physical factors such as mass and stiffness. The mass per unit area of a material is the most important factor in controlling the transmission of sound through the material. The so-called mass law is worth repeating here, as it applies to most materials at most frequencies:TL=20 log10(msf)−48.                where: TL=transmission loss (dB)        ms=mass per unit area (kg/m2)        f=frequency of the sound (Hz)        
Stiffness of the material is another factor that influences TL. Stiffer materials exhibit “coincidence dips” which are not explained by the above mass law. The coincidence or critical frequency is shown by:fc=A/t                 where: A is a constant for a material        t is the thickness of the material (mm)        
An example of a composition that is commonly used to produce sheet material with sound dampening properties is what is termed a loaded vinyl. In such a composition, a material with a high density is combined with vinyl at formulation stage. The resulting product has a high density whilst still maintaining high flexibility and thereby providing sound dampening properties.
However, vinyl is a product derived from petroleum sources so its cost and production is directly linked to the oil price and dictated by oil supply. Furthermore, vinyl does not biodegrade easily and in addition produces toxic fumes when burnt. This poses a particular problem when a loaded vinyl is used in building applications.
Accordingly, there is a need for an alternative material that may be used to produce a sheet material with sound dampening properties and which overcomes the disadvantages of loaded vinyl.
One attempt at providing such a material is described in WO 2006/053393 which describes a composition for producing a sheet material consisting of water, gelatine, glycerine and a filler material. However, it was found that the sheet material produced from such a composition was not stable at temperatures above 25° C., particularly when packaged immediately after manufacturing and then exposed to the sun. The material was found to melt and lose shape, providing undesirable characteristics when using this material in building applications.
The present invention seeks to provide a composition for producing sheet material with sound dampening properties which addresses the issues outlined above. The present invention also seeks to provide a process for producing such a sheet material.